In industrial filling plants, beverages are packaged in containers or bottles that are moved from one treatment area to another. Then they are typically loaded as groups into upwardly open bins or cases that are of parallepipedal shape and have vertical side walls formed with throughgoing holes. Typical a dozen bottles are held in a single such case, which itself is made of one piece of injection-molded plastic.
When machines handle such beverage cases, so-called hook grab systems are used by means of which at least one beverage case may be picked up by at least two or more hook grabs that are pivoted from above into the side holes so that the case can be lifted. Depending on the case size and the pack formation and/or the layer pattern of the cases, the hooks are arrayed in groups. In conventional hook grab systems, these hook groups are mounted on a common pivotal shaft that is centrally driven by a common drive and may thus carry out the desired pivoting movements.
DE 27 35 791 discloses a grab apparatus for lifting a plurality of bottle cases that are directly adjacent one other but not connected together. The grab apparatus comprises several pivotal hooks that engage through openings in side walls of the cases. The four walls of the bottle cases are associated with respective hooks, and all the hooks for an aligned row of case side walls are carried on a common pivot shaft. Two groups of parallel pivot shafts extending at a right angle to each other are positioned in two horizontal planes situated one above the other. The two groups of pivot shafts arranged one above the other are supported by each other at least where they cross. Every two adjacent, aligned pivot shafts has a common rotary drive.
DE 30 24 192 A1 further discloses a grab apparatus for loading and depalletizing piece goods, such as bottle cases, in planar layers from above. The apparatus has a central drive and adjustable force transmission elements.
In this context, various types of grab apparatuses are known for engaging cases, for example spring-loaded single hooks or grabs that are inserted from above along two walls of adjacent cases and that are then closed so that the tight engagement of the cases is based on friction. For example, EP 1 020 395 B1 discloses a clamp-type gripper for loads to be gripped from above. This document describes a grab capable of gripping a load without having to engage underneath it. When the support is raised with the gripping elements engaging the load, the grip automatically bears on the case(s) with a clamping force dependent on the weight of the load by the gripping elements moving in the load direction relative to the support elements. This device is only usable due to the establishment of a frictional grip.
DE 20 2005 007 347 U1 discloses a robot for engaging and transporting a container provided with a connector that itself has a horizontal support that may establish a connection with a robot. In this device, at least one vertical support arm is pivotally connected to the support element, and there is a connecting element adapted to the container at the end of the support arm facing away from the support element. By pivoting the support arm, the container may be connected to or disconnected from the connecting element. However, this device can only work with containers of the same size.
DE 22 53 185 A describes a grab apparatus for simultaneously engaging several bottle cases that are open at the top and provided with side holes for manual gripping. The device for engaging the cases may be controlled with respect to height and side position and is provided with grab arms in the form of hooks that may be pivoted into the recesses or holes for manual gripping and operated by means of hydraulic cylinders. The grab arms are positioned on push and/or pull rods that may be designed to be adjustable in several directions in one plane.
The known grab apparatuses require a defined shape of the objects to be gripped and additionally have to be guided and controlled in a precise way in order to be capable of reliable and safe gripping of the objects.